The present invention relates to a combination of a needle driving unit with needle driving means and a bending unit with bending means for bending the needle in order to bind a set of sheets stacked together.
In particular, the present invention relates to a stapling device in which the needle driving unit and the bending unit are stably moved in a sheet width direction of the set of the sheets to carry out a stapling process at any position, and a needle driving mechanism or bending mechanism in these units is improved to miniaturize the entire device.
Heretofore, various stapling devices for automatically stapling a set of sheets to bind the same have been proposed. In case this kind of stapling device is adopted to an image forming apparatus, such as a printer or a copier, it is structured that sheets ejected from an image forming section are stacked into a set or bundle, and a needle is automatically driven to a predetermined position of the set of the sheets to operate the binding process.
In the stapling device proposed in recent years, in order to provide the stapling process not only to a corner portion of the set of the sheets or a sheet side edge portion, but also to a center portion of the set of the sheets or any plural positions thereof, there has been proposed a stapling device in which a needle driving unit and a needle bending unit are separated on both sides of a sheet set passageway.
For example, the stapling devices in this kind have been disclosed in U.S. Pat. No. 5,806,750 corresponding to Japanese Patent Publication (KOKAI) No. 9-136302; U.S. Pat. No. 5,799,935 corresponding to Japanese Patent Publication (KOKAI) No. 9-136303; U.S. Pat. No. 5,662,318 corresponding to Japanese Patent Publication (KOKAI) NO. 8-108377; and Japanese Utility Model Publication (KOKAI) No. 6-63342.
In these stapling devices described above, especially, in a stapling device disclosed in U.S. Pat. No. 5,806,750 or a stapling device disclosed in U.S. Pat. No. 5,799,935, as shown in FIG. 12, a stapler S includes a needle driving unit 100 which drives a needle into a set of sheets, and a bending unit 101 for inwardly bending distal ends of the needle driven in the set of the sheets to thereby staple the same, and has a mechanism such that the set of the sheets sent between the needle driving unit 100 and the bending unit 101 is clamped between both the units 100 and 101 by moving both or one of the needle driving unit 100 and the bending unit 101, to thereby drive the needle into the set of the sheets.
Here, in order to move the needle driving unit 100 and the bending unit 101 in a sheet width direction, the aforementioned stapler S includes a pair of guide shafts 102F and 102R provided at the front and rear sides of the needle driving unit 100 in a lower side, and a pair of guide shafts 103F and 103R provided at the front and rear sides of the bending unit 101 in an upper side. Also, at the rear side of the rear guide shafts 102R and 103R, there are disposed moving shafts 104 and 105 for transmitting forces to move the needle driving unit 100 and the bending unit 101 in a sheet width direction from outside thereof.
Also, in other structures disclosed in other patent publications described above, similarly, at the rear sides of the guide shafts, moving forces for moving the needle driving unit and the bending unit in the sheet width direction are applied from outside.
Therefore, in the stapling devices disclosed in the patent publications described above, since the moving force is applied to a side end outside each unit, in case of moving the unit along the guide shaft, a moving force in the direction of inclining the unit with respect to the guide shaft always works, so that an unnecessary resistance force may work between the unit and the guide shaft. Accordingly, a movement in the sheet width direction may not be made stably and smoothly.
Also, in the stapling device described above, since the moving shafts for moving the units in the sheet width direction are disposed outside the units and the guide shafts for guiding the movements of the units, a large space is required for installing a driving transmission mechanism or the like for driving the moving shafts, so that the miniaturization of the entire device can not be fully achieved.
Further, in the conventional stapling device, in case, for example, needle bending means in the unit is moved in the sheet thickness direction, a vertical movement of the needle bending means is made by a cam through a lever, and a large space for the cam, the lever or the like is required between the cam and the needle bending means. Especially, in case a stapling process is carried out for a set of sheets ranged from a small number of sheets to a large number of sheets, an area for vertical movement of the bending means must be enlarged. Thus, an interlocking movement mechanism formed of the cam and a lever mechanism has to be complicated, or the lever or the cam itself must be enlarged, so that a space for disposing or arranging the interlocking mechanism, such as the lever, must be enlarged between the cam and the bending means, resulting in further increasing a size of the entire device.
Thus, in the recent progress of further miniaturizing the image forming apparatus to which the stapling device is applied, the aforementioned stapling device can not respond to the demand of miniaturizing the stapling device.
Accordingly, an object of the present invention is to provide a stapling device in which a needle driving unit and a needle bending unit can be moved stably and smoothly in case these units are moved in a sheet width direction, and guide shafts and moving shafts as mechanisms for moving these units are disposed rationally, to thereby achieve a miniaturization of the entire device.
Another object of the invention is to provide a stapling device as stated above, in which a space for moving the needle bending means or the like in the sheet thickness direction is reduced as small as possible, to thereby achieve the miniaturization of the entire device.
A further object of the invention is to provide a stapling device as stated above, which can be applied to a small size image processing apparatus, and in this case, the set of the sheets can be securely stapled at a stapling position.
Further objects and advantages of the invention will be apparent from the following description of the invention.
To achieve the aforementioned objects, the present invention provides a stapling device, comprising: a needle driving unit for driving a needle into a set of sheets; a bending unit for bending the needle driven into the set of the sheets; two pairs of front and rear guide shafts for respectively supporting the needle driving unit and the bending unit and guiding movements of these units in a sheet width direction; and moving shafts for moving the needle driving unit and the bending unit along the guide shafts in the sheet width direction, wherein the respective moving shafts are disposed between the front and rear guide shafts. Therefore, movements of the respective units in the sheet width direction can be operated stably and smoothly, and since the moving shafts are disposed between the front and rear guide shafts, the entire device can be structured compact.
Also, in the stapling device as stated above, one of the front and rear guide shafts disposed in each of the needle driving unit and the bending unit is also used as a driving shaft for a needle driving operation or a bending operation. Accordingly, it is not necessary to provide an additional moving mechanism, to thereby achieve the further miniaturization of the device.
Further, between the needle driving unit and the bending unit, there are disposed sheet path guide members extending between the front and rear guide shafts, and the sheet path guide members are attached to spring members wound around the guide shaft. The spring member is expanded or contracted in accordance with the movement of the needle driving unit and the bending unit along the guide shafts, and the sheet path guide member moves in an axial direction of the guide shafts by the expansion or contraction of the spring member. Therefore, even if the sheet in the set of the sheets is curled, the set of the sheets can be guided by the sheet path guide members, so that the set of the sheets can be securely stapled.
Also, in at least one of the needle driving unit and the bending unit, there are disposed a movable frame for supporting at least one of needle driving means and bending means; a base frame for supporting the movable frame to be movable in a sheet thickness direction; and cam means for moving the movable frame in the sheet thickness direction, wherein the cam means is disposed in one of the base frame and the movable frame. Accordingly, a space for a moving mechanism for moving the needle bending means or the like in the sheet thickness direction is reduced as small as possible, to thereby achieve the miniaturization of the entire device.